The present invention relates to a scroll compressor for a refrigeration cycle handling, for example, a hydrofluorocarbon (HFC) refrigerant, a natural refrigerant such as air or carbon dioxide, or a compressed gas. The present invention is particularly suitable for application to a scroll compressor having a high-pressure (approximately equal to a discharge pressure) back pressure chamber (high pressure hydraulic chamber) formed on the back side of an orbiting scroll and a back pressure chamber kept at an intermediate pressure lower than the discharge pressure or at an intake pressure with the two chambers at different pressures partitioned pressure-wise by a sealing part.
Scroll compressors are widely used for refrigerators and air-conditioners in various fields. Compared with other types of compressors such as reciprocating compressors and rotary compressors, scroll compressors are said to be superior in various characteristics, for example, operational efficiency, reliability, and quietness.
Scroll compressors are disclosed, for example, in JP-A No. 2003-176794 and JP-A No. 2004-19499.
In the scroll compressor disclosed in JP-A No. 2003-176794, a high-pressure back pressure chamber (high pressure hydraulic chamber) formed around a central portion on the back side of an orbiting scroll and a low-pressure (intake pressure or intermediate pressure) back pressure chamber formed in an outer peripheral portion are sealed by a sealing part provided on a frame end surface facing a boss-portion end surface on the back side of the orbiting scroll. In the scroll compressor, the boss-portion end surface has small holes for holding lubricating oil coming from the high pressure hydraulic chamber, and, by making the orbiting scroll engage in orbital motion to cause the small holes holding lubricating oil to move back and forth across the sealing part, lubricating oil is intermittently supplied from the high pressure hydraulic chamber to the low-pressure back pressure chamber formed in an outer peripheral portion. The lubricating oil thus supplied to the low-pressure back pressure chamber lubricates sliding parts such as an Oldham's ring, then enters a compression chamber from its intake side to lubricate the scroll wraps engaged with each other to be subsequently discharged, together with the compressed refrigerant, through a discharge port.
In the scroll compressor disclosed in JP-A No. 2003-176794, the amount of lubricating oil supplied from the high pressure hydraulic chamber to the back pressure chamber (low pressure chamber) can be adjusted by changing the size of the small holes. The leakage of lubricant oil into the low pressure chamber can therefore be easily adjusted to an appropriate amount, and the efficiency and reliability of the scroll compressor can be improved.
In the scroll compressor disclosed in JP-A No. 2004-19499, a lubricating oil reservoir (high pressure hydraulic chamber) provided in a central portion on the back side of the orbiting scroll and a low-pressure back pressure chamber provided in an outer peripheral portion are communicated with each other through an oil supply passage made up of a small hole (with a diameter of 0.2 to 0.5 mm) and a long hole. The orbiting scroll is made to orbitally move, thereby, causing the lubricating oil inlet of the small hole to move back and forth across an annular sealing member. This intermittently communicates the high pressure hydraulic chamber and the low-pressure back pressure chamber causing lubricating oil to be supplied from the lubricating oil reservoir to the back pressure chamber. According to JP-A No. 2004-19499, this arrangement makes it possible to appropriately control the amount of lubricating oil which tends to be supplied excessively due to a large differential pressure.